on Jul 11th, 2009Testing hard to test code with EasyMock

If you are into unit testing, you may find EasyMock quite useful. It is very valuable for making hard-to-test-code testable.

For example I recently was adding tab-switching via keyboard to Riena. The state of each tab is kept in an interface named INavigationNode which has about 40 methods (!). Creating a mock by hand for such a big interface would not be fun at all. With EasyMock it just takes is a call to:

ISubApplicationNode nodeA = EasyMock.createMock(ISubApplicationNode.class);

The code for determining the next tab, depends strictly on the isSelected property. Manipulating the return value of this method takes just another EasyMock call:

EasyMock.expect(nodeA.isSelected()).andReturn(true);

This tells EasyMock that nodeA.isSelected() will be called once and should return true.

After everything is set-up I switch from ‘record’ to ‘play-back’ mode:

EasyMock.replay(nodeA);

Here’s a full example of a test case:

  protected void setUp() throws Exception {
    super.setUp();
    handler = new SwitchSubApplication();
    nodeA = EasyMock.createMock(ISubApplicationNode.class);
    nodeB = EasyMock.createMock(ISubApplicationNode.class);
    nodeC = EasyMock.createMock(ISubApplicationNode.class);
  }
 
  public void testFindNextSubApplicationAtoB() {
    EasyMock.expect(nodeA.isSelected()).andReturn(true);
    EasyMock.replay(nodeA);
 
    ISubApplicationNode[] nodes = { nodeA, nodeB, nodeC };
    assertSame(nodeB, handler.findNextNode(nodes));
  }

This post barely scratches the surface. Curious? Read this nice EasyMock introduction.

Image: (c) *Micky/flickr. Licensed under creative commons.

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Tags: riena, testing, tips

3 responses so far Elias Volanakis syndicate

3 Responses to “Testing hard to test code with EasyMock”

1. Marek Romanowski says:

   July 11, 2009 at 8:58 am

   If you tried EasyMock and you find it useful, then try Mockito too. I’ve been using both libraries and find Mockito a little bit more developer friendly (in term of writing code). Project is availible at mockito.org (http://code.google.com/p/mockito/).
2. Robert Konigsberg says:

   July 11, 2009 at 7:41 pm

   I’m starting to use EasyMock; it’s pretty nice, if a little messy. The classextension package has some really nice behavior.
3. Carlus says:

   July 13, 2009 at 6:16 pm

   Love EasyMock. It is absolutely great.

   Something that I would recommend is the use of the IMockControl object. Using the IMockControl, you code can change from this:

   EasyMock.replay(nodeA);
   EasyMock.replay(nodeB);
   EasyMock.replay(nodeC);

   // execute logic….

   EasyMock.verify(nodeA);
   EasyMock.verify(nodeB)
   EasyMock.verify(nodeC)

   To this:

   setup() {
   mockControl = EasyMock.createControl();
   nodeA = mockControl.createMock(ISubApplicationNode.class);
   nodeB = mockControl.createMock(ISubApplicationNode.class);
   nodeC = mockControl.createMock(ISubApplicationNode.class);
   }

   testX() {
   expect(nodeA).andReturn();
   expect(nodeB).andReturn();

   …
   mockControl.replay();

   // execute logic

   mockControl.verify();

   }

   Found this niceness by asking questions on the mailing list….

   Enjoy…